Opening:
The opening should be plum, level and square and ½ inch larger than the window in height and weight. This does not include the nailing fin. Keep the window in the “locking position” during installation to prevent sash movement.
Apply 1/2 inch of quality grade silicon caulking to the interior side of the nailing fin, sealing the fin to the house exterior wrap.
Setting the window
Make sure the window sill is supported with a straight and level position shims all around the bottom sill. Adjust shims to be equal on both sides. Hammer one upper corner to keep window in place. This allows you to check the shims and level the window properly. Shims should be smug along the entire window and window should be completely leveled. When completed and done properly all meeting rail should align and latches should lock smoothly.
Finally, using one inch stainless steel nails secure the entire window. Using all of the slotted holes on the nailing fin. Used appropriate self-adhesive flashing all around the unit. Begin with the head and continue all around making sure flashing overlap each other. Install batt insulation between the window and opening. Careful not to overstuff or use other material such as expanding form for this may cause the window to warp.